Power module, power converter and manufacturing method of power module

ABSTRACT

A power module includes a heat-dissipating substrate, a first planar power device and a second planar power device. The first planar power device includes a plurality of electrodes disposed on an upper surface of the first planar power device. The second planar power device includes a plurality of electrodes disposed on an upper surface of the second planar power device. Lower surfaces of the first planar power device and the second planar power device are disposed on the heat-dissipating substrate.

RELATED APPLICATIONS

This application claims priority to China Application Serial Number201310694495.8 filed Dec. 16, 2013, which is herein incorporated byreference.

BACKGROUND

1. Field of Invention

The present invention relates to a power module. More particularly, thepresent invention relates to a power module used in a POWER converter.

2. Description of Related Art

High efficiency and high power density has been the industry'srequirements for power converters. High efficiency means less energyconsumption, and energy saving helps to reduce carbon and protectenvironment. High power density stands for small size, lightweight andless space requirement, thereby reducing costs.

The energy consumption of the power converter is mainly composed of anon-state loss and a switch loss, especially the switch loss of an activedevice. The switch loss is more significantly affected by a workingfrequency. The power converter, especially the switch power converter,has the working frequency usually higher than 20 kHz in order todecrease audio noise. The selection of an actual working frequency ofthe power converter is more significantly affected by an inactivedevice, especially a magnetic element. If the magnetic element has asmall size, a high frequency is usually needed to decrease the magneticflux density of the magnetic element in order to achieve reliable work,thus inducing a high switch loss. Alternatively, the wire diameter ofthe wire set can be decreased and the number of loops in the magneticelement can be increased to increase the on-state loss.

On the contrary, if the magnetic element has a large size, the workingfrequency can be lowered under the precondition of assuring the reliablework, thus decreasing the switch loss. Also, the wire diameter of thewire set can be increased or the number of loops in the magnetic elementmay be decreased to decrease the on-state loss, thus decreasing theoverall loss and obtaining high efficiency.

Therefore, one of the key factors of obtaining the high power density orthe high efficiency is to enhance the space availability inside thepower converter. As the space availability gets higher, the larger spaceis left for the inactive device, such as the magnetic element, acapacitor or the like, in which the inactive device is very important tothe power converting efficiency. Thus, the large-size inactive elementcan be easily used to increase the power efficiency. Also, the totalpower of the power source can be increased by using the large-sizeinactive device, so that the power density of the power converter can beenhanced. Thus, for the high power space availability, the highefficiency can be achieved more easily under the specific power density,or the high power density can be achieved more easily under the specificefficiency, and it is possible to possess both the high power densityand the high efficiency concurrently.

In addition, a semiconductor device is one of the important factors fordetermining the efficiency of the power converter. However, the use ofthe semiconductor device tends to unavoidably need to use additionalmaterials, such as a packaging material for protecting the semiconductordevice, a heat sink for heat dissipating, a fixture for fixing thesemiconductor device, and the like. As the ratio of these materialsinside the power converter gets greater, the internal space availabilityof the power converter gets worse. As a result, the ratio of the space,occupied by the power semiconductor device, to the total size of thepower converter gets larger and larger, and gets more and moreemphasized. In order to enhance the performance of the power converter,the space availability of the power converter has to be continuouslyenhanced. The package space availability of the semiconductor devicebecomes a bottleneck.

For an integrated power module (IPM), many semiconductor devices (e.g. apower device, a controlling device, a driving device) are integratedwithin a device package for the enhancement of the space availabilitywithin the device package. The power module has the advantages includinguse convenience and long average operation time without faults, etc.,and is widely applied to various occasions. Because the power module hasmany power chips integrated together, a lot of heat is generated anddistributed in many points of the power module. The thermal managementthereof thus becomes very important. There are many existing arts forimproving the heat dissipating ability of the IPM.

Referring to FIG. 1 a, FIG. 1 a is a schematic diagram showing aconventional power module 100 a. As shown in FIG. 1 a, the power module100 a includes a first power device 11, a second power device 12, asubstrate 13, a bonding wire 14, a lead frame 15, and a molding material16. The substrate 13 is a direct bonded copper (DBC) ceramic substrate,which is made from a copper layer 131 with good thermal conductivity anda ceramic substrate 132 with high insulation. A circuit pattern isformed on the DCB ceramic substrate, and then the respective powerdevices 11 and 12 are assembled with the DBC ceramic substrate. Then,with respect to parts of the electrodes on the first power device 11 andthe second power device 12, the bonding wire 14 is adopted to accomplishthe electrical connections between the front-side electrodes of thefirst/the second power devices 11, 12 and the DBC substrate and the leadframe 15. Thereafter, a molding material 16 is injected to enclose theareas desired to be protected, thus achieving dustproof, moisture-proofand insulation functions.

However, because all of the power devices have to be mounted on the DBCceramic substrate, the DBC ceramic substrate with a larger area isrequired. However, the DBC ceramic substrate is relatively expensive,thus increasing the cost of the entire package module. In addition, theDBC ceramic substrate 132 is generally formed from aluminum oxide ofwhich the coefficient of heat conductivity is equal to about 24 W/m·K,which is a great improvement with respect to the molding material (ofwhich the coefficient of heat conductivity is generally lower than 1W/m·K). However, the heat conducive property of aluminum oxide is stillworse than that of metal (e.g., the coefficient of heat conductivity ofcopper is equal to about 400 W/m·K), so that the transversal heatdiffusion ability of the DBC ceramic substrate is not good enough, andthe poor thermal uniformity thereof tends to occur. Thus, in theconventional method, additional heat sink is added to expand the heatdissipating area and improving the thermal uniformity.

Referring to FIG. 1 b, FIG. 1 b is a schematic diagram showing anotherconventional power module 100 b. Similar to the first power module 100 ashown in FIG. 1 a, the power device 100 b includes the first powerdevice 11, the second power device 12, and the substrate 13, in whichthe substrate 13 is a DBC ceramic substrate, and the first power device11 and the second power device 12 are disposed on the substrate 13.Another side of the substrate 13 is disposed on the heat-dissipatingunit 17 (e.g. a heat sink). The heat sink can be formed from goodthermo-conductive materials, such as copper, aluminum, graphite or thelike, so that the thermal uniformity performance of the power module 100b can be greatly increased.

Because the DBC ceramic substrate has high stress withstand capacity, athicker molding material is required to ensure the overall insulationand stress withstand capacities. Because the heat dissipating ability ofthe DBC ceramic substrate is better, the DBC ceramic substrate is oftendesigned for the application with a higher thermal density, and screwsare adopted to fix the additional heat sinks. Because of high stresswithstand packaging, the corresponding screws holes also need to bedesigned for stress withstanding, and thus occupies larger actual space.For example, a screw hole with a 3 mm hole diameter generally occupiesan area of which the diameter is greater than 5 mm for meeting thestress withstanding requirements of the power module, thus lowering thespace availability of the power module.

Furthermore, the power device 100 b also includes a controlling/drivingdevice 18. Because the controlling device and the driving device have alow energy consumption, and are relatively sensitive to temperature,they are usually disposed on the heat-dissipating unit 17 through athermal insulating layer 19 (such as a printed circuit board (PCB), amolding material or the like). The thermal conductive insulating layer19 can be formed by adhering, filling, or coating on the surface.Thereafter, the wire bonding is performed to accomplish the electricalconnections among the first power device 11, the second power device 12,the controlling/driving device 18, the substrate 13 and the lead frame15, and then the molding material 16 is injected to complete thefabrication of the packaging of the power module 100 b. Accordingly, thedevice with low power consumption and being sensitive to heat can beintegrated into the power module with less high-temperature influencefrom the power device, thereby improving the space availability of thepower module.

Although the space availability of the power module can be enhanced bydisposing the controlling device or driving device on the heat sinkthrough thermal insulating layer, the aforementioned problems of the DBCceramic substrate still cannot be overcome. Besides, the shell of thepower module (not shown in FIG. 1 b) is generally designed to beinsulated to simplify the installation and selection of the heat sink.Hence, even if the material of the shell is a good electrical conductor(e.g., copper), the shell is still designed to be electricallyinsulated. Thus, the metal material (such as copper) in the power moduleis merely used to provide one single function of electrical or thermalconduction, and its electrically and thermally conductive properties arenot utilized simultaneously, thus not fully utilizing the features ofthe material.

In sum, the conventional power modules still have various problems suchas poor heat dissipating performance, material wastage, the difficultyof reliability design, not fully utilized electrical performance, theover design caused by over-emphasis on generality, and poor economicperformance, etc. More particularly, the conventional power modules haveinsufficient space availability, and their applications in high powerdensity or high efficiency occasions are thus restricted. In order tofurther increase the power density or converting efficiency of the powerconverter, there is a need to develop a power module with high spaceavailability and reasonable cost.

SUMMARY

To solve the above problems, the present disclosure provides a powermodule with higher space availability, in which the power module isformed by disposing planar power devices directly on a heat-dissipatingsubstrate, thereby not only effectively increasing the spaceavailability but also saving the cost of additionally a DBC ceramicsubstrate and also increasing the heat dissipation of the power modulesuch that the high power density or high efficiency of a power convertercan be achieved, and the electric energy conversion efficiency of thepower converter can be effectively enhanced.

An aspect of this disclosure provides a power module. The power moduleincludes a heat-dissipating substrate, a first planar power device, anda second planar power device. The first planar power device includes aplurality of electrodes on an upper surface of the first planar powerdevice, and the second planar power device includes a plurality ofelectrodes on an upper surface of the second planar power device, and alower surface of the first planar power device and a lower surface ofthe second planar power device are disposed above the heat-dissipatingsubstrate.

According to another aspect of the present invention, a power converteris provided and includes the aforementioned power module, a power inputterminal, and a power output terminal. The power input terminal isconnected to the power module, and the power output terminal isconnected to the power module. An input voltage is received by the powerinput terminal and converted by the power module into an output voltageoutputted through the power output terminal.

According to another aspect of the present invention provides a methodof manufacturing a power module, the method including: providing a firstplanar power device, a second planar power device and a heat-dissipatingsubstrate, and disposing the first planar power device and the secondplanar power device on an upper of the heat-dissipating substrate;providing an insulating layer and disposing at least one planar device,at least one capacitor and a plurality of pins on the insulting layer;covering the heat-dissipating substrate with the insulating layer, andenabling the insulating layer to cover the first planar power device andthe second planar power device; and connecting the first planar powerdevice, the second planar power device, at least one planar device andat least one capacitor to the corresponding positions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the followingdetailed description of the embodiment, with reference made to theaccompanying drawings as follows:

FIG. 1 a is a schematic diagram showing the conventional power module;FIG. 1 b is a schematic diagram showing another conventional powermodule;

FIG. 2 a is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 2 b is a schematic top view showing a power module according toFIG. 2 a;

FIG. 2 c is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 2 d is a schematic top view showing a power module according toFIG. 2 c;

FIG. 2 e shows a circuit diagram of a half-bridge converter according toan embodiment of the present invention;

FIG. 2 f is a schematic cross-sectional view showing a power moduleaccording to another embodiment of the present invention;

FIG. 3 is a schematic diagram showing a gallium-nitride (GaN) powerdevice according to an embodiment of the present invention;

FIG. 4 a shows a circuit diagram of another half-bridge converteraccording to an embodiment of the present invention;

FIG. 4 b is a schematic cross-sectional view showing a power moduleaccording to FIG. 4 a;

FIG. 4 c is a schematic top view showing a power module according toFIG. 4 b;

FIG. 4 d is a schematic cross-sectional view showing another powermodule according to FIG. 4 a;

FIG. 4 e is a schematic top view showing a power module according toFIG. 4 d;

FIG. 4 f is a schematic cross-sectional view showing another powermodule according to FIG. 4 a;

FIG. 4 g is a schematic top view showing a power module according toFIG. 4 f;

FIG. 4 h is another schematic cross-sectional view showing a powermodule according to FIG. 4 a;

FIG. 5 a shows a circuit diagram of half-bridge converter according toan embodiment of the present invention;

FIG. 5 b shows a circuit diagram according to an embodiment of thepresent invention;

FIG. 6 shows a circuit diagram of a power module according to anembodiment of the present invention;

FIG. 7 shows a circuit diagram of a switching device according to anembodiment of the present invention;

FIG. 8 a is a schematic cross-sectional view showing a circuit diagramaccording to FIG. 6;

FIG. 8 b is a schematic top view showing a power module according toFIG. 8 a;

FIG. 8 c is a schematic cross-sectional view of a power module accordingto the circuit diagram of FIG. 6;

FIG. 8 d is a schematic cross-sectional view of a power module accordingto the circuit diagram of FIG. 6;

FIG. 9 is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 a is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 b is a schematic top view showing a power module according toFIG. 10 a;

FIG. 10 c is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 d is a schematic top view showing a power module according toFIG. 10 c;

FIG. 10 e is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 f is a schematic top view showing a power module according toFIG. 10 e;

FIG. 10 g is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 h is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 10 i is a schematic cross-sectional view showing a power moduleaccording to an embodiment of the present invention;

FIG. 11 is a schematic diagram showing a power converter according to anembodiment of the present invention;

FIG. 12 a is a schematic diagram showing a power converter according toan embodiment of the present invention;

FIG. 12 b is a schematic diagram showing a power converter according toan embodiment of the present invention;

FIGS. 13 a to 13 f are schematic diagrams showing processes ofmanufacturing power modules according to an embodiment of the presentinvention; and

FIG. 14 shows a half-bridge circuit according to an embodiment of thepresent invention.

DETAILED DESCRIPTION

Specific embodiments of the present invention are further described indetail below with reference to the accompanying drawings, however, theembodiments described are not intended to limit the present inventionand it is not intended for the description of operation to limit theorder of implementation. Moreover, any device with equivalent functionsthat is produced from a structure formed by a recombination of elementsshall fall within the scope of the present invention. Additionally, thedrawings are only illustrative and are not drawn to actual size.

Referring to FIG. 2 a and FIG. 2 b, FIG. 2 a is a schematiccross-sectional view showing a power module 200 a according to anembodiment of the present invention, and FIG. 2 b is a schematic topview showing a power module 200 a according to FIG. 2 a. As shown inFIG. 2 a and FIG. 2 b, the power module 200 a includes at least onefirst planar power device 21, at least one second planar power device22, a heat-dissipating substrate 23 and a plurality of pins 24. Forconvenience and clarity of explanation, the present embodiment and thefollowing embodiments all use two planar power devices as an example forexplanation, but the embodiments are not limited thereto. A gate G₁ ofthe first planar power device 21, a drain D₁ and a source S₁ are locatedon an upper surface of the first planar power device 21; and a gate G₂of the second planar power device 22, a drain D₂ and a source S₂ arelocated on an upper surface of the second planar power device 22. In anembodiment of present invention, a coating or dispensing technique isused to apply solder or an adhesive to lower surfaces of the firstplanar power device 21 and the second planar power device 22. The lowersurface of the first planar power device 21 and the lower surface of thesecond planar power device 22 are disposed on the heat-dissipatingsubstrate 23 through the methods with better thermal conductivecapabilities such as soldering, bonding or the like. Theheat-dissipating substrate 23 can be a heat sink made from anelectro-conductive material, such as copper, aluminum, graphite or thelike. In this embodiment, the first planar power device 21 and thesecond planar power device 22 are integrated with the heat-dissipatingsubstrate 23 by solder 25, but this embodiment is not limited to thisconnection method. For convenient explanation, the following embodimentsall use the soldering method to connect respective power devices on theheat-dissipating substrate, but the embodiments are not limited thereto.

Referring to FIG. 3, FIG. 3 is a schematic diagram showing agallium-nitride (GaN) power device 300 according to an embodiment of thepresent invention, in which the GaN power device 300 can be used as thefirst planar power device 21 and the second planar power device 22 inFIG. 2 a and FIG. 2 b. As shown in FIG. 3, the GaN power device 300 isgenerally a planar device, which is different from a vertical-type powerdevice using a silicon material or silicon carbide (SiC) material. TheGaN power device 300 includes three electrodes formed from agallium-nitride (GaN) material layer 31, which are a gate G, a drain Dand a source S distributed on the same plane. It is noted that, theplanar device of the present invention means that all electrodes aredisposed toward the same direction. In other words, all electrodes aredisposed on the upper surface of the planar device, and no electrode isdisposed on the lower surface of the planar device. In addition, the GaNpower device 300 further includes a substrate 32. The substrate 32 isgenerally formed from silicon or silicon carbide for supporting the GaNmaterial layer 31. A first insulating layer 33 is disposed between theGaN material layer 31 and the substrate 32 for providing voltagewithstand capacity and electrical insulation properties for the GaNpower device 300. Moreover, a second insulating layer 34 is disposedamong the three electrodes for providing electrical insulation among thegate G, the drain D and the source S. Moreover, a certain extent ofelectrical insulation should be satisfied among the three electrodes ofthe GaN power device 300 and the lower surface of the substrate 32.Thus, all of the electrodes of the GaN power device 300 are disposed onthe upper surface of the GaN power device 300, and the lower surface ofthe GaN power device 300 has the electrical insulation property and isnot used for electrical conduction.

Returning to FIG. 2 a and FIG. 2 b, the power module 200 a includes thefirst planar power device 21 and the second planar power device 22, inwhich at least one of the two planar power devices 21 and 22 is the GaNpower device 300 shown in FIG. 3. In this embodiment, both of the firstplanar power device 21 and the second planar power device 22 are GaNpower devices, but this embodiment is not limited thereto. Forconvenience and clarity of explanation, the first planar power deviceand the second planar power device in the following embodiments are GaNpower devices, but the embodiments are not limited thereto.

In addition, at least one of the first planar power device 21 and thesecond planar power device 22 is an active power device. The so-calledactive power device is a power switch having a control terminal. Forexample, the power switch is a switch unit such as ametal-oxide-semiconductor field-effect transistor (MOSFET), an insulatedgate bipolar transistor (IGBT) or the like. The other one of the planarpower devices also can be an active power device, or a passive powerdevice such as a diode. Furthermore, at least one of the two planarpower devices is an active switch device with at least three electrodes.

Due to the basic insulation and stress withstand capacities existingbetween the electrodes of the GaN power device and the substrate, thatis, an electrically insulating thermal conductor is formed inside theGaN power device, the first planar power device 21 and the second planarpower device 22 can be directly disposed on the heat-dissipatingsubstrate 23, and the first planar power device 21 and the second planarpower device 22 can be connected to the upper surface of theheat-dissipating substrate 23 through the solder 25, but this embodimentis not limited to this connection method. In other words, there is noneed to dispose an additional electrical insulating material between thefirst/the second planar power devices 21, 22 and the heat-dissipatingsubstrate 23, and the effect of the electrical insulation between thefirst planar power device 21 and the second planar power device 22 canbe achieved.

In the conventional packaging process of a vertical-type power device,in order to electrically isolate two power devices, an additionalelectrically insulating thermal-conductor (e.g. Direct Bonded Copper,DBC) has to be disposed between the heat-dissipating substrate and thevertical-type power device. In this embodiment, the power module 200 aadopts the GaN power device 300 of FIG. 3, thus omitting the additionalelectrically insulating thermal-conductor (e.g. Direct Bonded Copper,DBC) for isolating the two power devices from the heat-dissipatingsubstrate in the packaging process. Thus, the structure of the powermodule 200 a not only saves the cost of electrically insulatingthermal-conductor, but also reduces the thermal resistance between thepower device and the heat-dissipating substrate. In addition, the spacepackaging the electrically insulating thermal-conductor can be saved,and the space availability of the power module can be advantageouslyincreased.

In FIG. 2 a and FIG. 2 b, the power module 200 a includes a plurality ofpins 24. As shown in FIG. 2 b, the gate G₁, the drain D₁ and the sourceS₁ of the first planar power device 21, and the gate G₂, the drain D₂and the source S₂ of the second planar power device 22 are respectivelyconnected to the corresponding pins 24. The first/second planar powerdevices 21, 22 and the pins 24 can be connected to each other by wirebonding or copper strap bonding or the like. In this embodiment, for thepower module 200 a, bonding wires are used to connect each electrode onthe first/the second planar power devices 21, 22 to the correspondingpins 24, but this embodiment is not limited thereto. Moreover, in thisembodiment, the gate G₁, the drain D₁ and the source S₁ of the firstplanar power device 21, and the gate G₂, the drain D₂ and the source S₂of the second planar power device 22 are electrically connected to thepins 24 of G₁, the pins 24 of D₁, the pins 24 of S₁, the pins 24 of G₂,the pins 24 of D₂, the pins 24 of S₂ through the bonding wires, and thesource S₁ of the first planar power device 21 is electrically connectedto the drain D₂ of the second planar power device 22 through the bondingwire 26. For convenience and clarity of explanation, the followingembodiments all adopt the wire bonding to connect each device to thepin, but the embodiments are not limited thereto.

After the electrical connections between each device and the pin iscompleted, a molding material is injected to cover an area desired to beprotected in the packaging process, so as to achieve dustproof,moisture-proof, and electrical insulation functions. For convenience andclarity of explanation, this step will be described again in thefollowing embodiments.

Because the heat-dissipating substrate 23 is a good electricalconductor, it also can be used as a large area electrode. Referring toFIG. 2 c and FIG. 2 d, FIG. 2 c is a schematic cross-sectional viewshowing a power module 200 b according to an embodiment of the presentinvention, and FIG. 2 d is a schematic top view showing a power module200 b according to FIG. 2 c. In FIG. 2 c and FIG. 2 d, the source S₂ ofthe second planar power device 22 is directly connected to theheat-dissipating substrate 23 through the wire bonding 26 but notconnected to the corresponding pin 24, and thus the amount of therequired pins 24 of the power module 200 b can be reduced. Further,because the electrical resistance and inductance of the heat-dissipatingsubstrate 23 used as an electrode are very small, when the source S2 ofthe second planar power device 22 is directly connected to theheat-dissipating substrate 23, not only the space availability of thepower module 200 b can be increased, but also the electrical propertycan be improved.

It is noted that, when the heat-dissipating substrate 23 is not used asan electrode, the heat-dissipating substrate 23 may not need to beformed from an electro-conductive material, that is, theheat-dissipating substrate 23 can also be an electrically insulatingthermal conductor. However, while the heat-dissipating substrate 23 isformed from an electro-conductive material, in order to use theconductive property effectively, the heat-dissipating substrate 23 canbe used as an electrode.

Because the heat-dissipating substrate has a large area and is likely tobe connected to a heat sink with a larger area outside the power module,the heat-dissipating substrate may easily form a larger capacitor withground and become a path of electromagnetic interference. Thus, theheat-dissipating substrate should be connected to a stable electroderelative to the ground. Referring to FIG. 2 e, FIG. 2 e shows a circuitdiagram of a half-bridge converter according to an embodiment of thepresent invention. As shown in FIG. 2 e, the half-bridge converter isconstructed by the first planar power device 21 and the second planarpower device 22, in which the first planar power device 21 and thesecond planar power device 22 both are active switch devices. In thepower module 200 b, the source S₁ of the first planar power device 21 isconnected to the drain D₂ of the second planar power device 22, andjointly connected to an output voltage pin Vo. In addition, the drain D₁of the first planar power device 21 is connected to a first inputvoltage pin Vbus+, the source S₂ of the second planar power device 22 isconnected to a second input voltage pin Vbus−, and the first inputvoltage pin Vbus+ and the second input voltage pin Vbus− arerespectively connected to the input power Vin, so as to realize thefunctions of the converter.

Referring to FIG. 2 d, the source S₁ of the first planar power device 21and the drain D2 of the second planar power device 22 are connected tothe output voltage pin Vo through the bonding wires. It should be notedthat, in this embodiment, the source S₁ of the first planar power device21 and the drain D₂ of the second planar power device 22 are connectedto two output voltage pins Vo through bonding wires. In addition, thedrain D₁ of the first planar power device 21 is connected to the firstinput voltage pin Vbus+ through a bonding wire, and the source S₂ of thesecond planar power device 22 is connected to the heat-dissipatingsubstrate 23 through a bonding wire. In this embodiment, theheat-dissipating substrate 23 can be used as the second input voltagepin Vbus− in FIG. 2 e. Moreover, the second input voltage pin Vbus− alsocan be added to the FIG. 2 d (not shown in FIG. 2 d), thereby connectingthe source S₂ of the second planar power device 22 to the second inputvoltage pin Vbus− through a bonding wire.

Further, the heat-dissipating substrate 23 of the power module 200 balso can be connected to the first input voltage pin Vbus+, that is, thedrain D₁ of the first planar power device 21 can also be connected tothe heat-dissipating substrate 23 through a bonding wire so as to beconnected to the first input voltage pin Vbus+, and the source S₂ of thesecond planar power device 22 is connected to the second input voltagepin Vbus− through a bonding wire. Briefly speaking, when theheat-dissipating substrate is used as one of the electrodes of the powermodule, besides having good anti-electromagnetic interferencecapability, the space availability and heat dissipating ability are alsoimproved. In addition, one pin used in the power module can be reducedso that the fabrication cost of the power module can be lowered.

Further, in the power module 200 b, the working voltage of the firstplanar power device 21 and that of the second planar power device 22 aredifferent, and the working voltage of the first planar power device 21is usually higher than that of the second planar power device 22(because the first planar power device 21 directly receives the inputvoltage Vin). Hence, to ensure the voltage withstand capacity betweenthe lower surface of the first planar power device 21 and its source S₁to be equivalent to the voltage withstand capacity between the drain D₁and the source S₁ of the first planar power device 21, an electricallyinsulating thermal conductive layer can be additionally disposed betweenthe first planar power device 21 and the heat-dissipating substrate 23.As shown in FIG. 2 f, FIG. 2 f is a schematic cross-sectional viewshowing a power module 200 c according to another embodiment of thepresent invention. An electrically insulating thermal conductive layer28 is disposed between the first planar power device 21 and theheat-dissipating substrate 23, thereby preventing the first planar powerdevice 21 from being damaged by the high voltage received by the powermodule 200 c. In addition, because the second planar power device 22does not directly receive the input voltage, and the voltage withstandcapacity of the second planar power device 22 does not have to be thesame as that of the first planar power device 21, the second planarpower device 22 can be directly disposed on the heat-dissipatingsubstrate 23.

Due to the high switching speed of the gallium-nitride (GaN) powerdevice, the equivalent inductance of the power module after beingpackaged will result in more switching loss, or when the switch is off,the stability of the power module will be affected because the voltageof the power device is too high. Therefore, for designing the converterin the FIG. 2 e, a capacitor is generally required to be disposed toreduce the equivalent loop inductance of the bridge in the converter.

Referring to FIG. 4 a, FIG. 4 a shows a circuit diagram of anotherhalf-bridge converter according to an embodiment of the presentinvention. As shown in FIG. 4 a, a power module 400 of a half-bridgeconverter further includes a capacitor C which is cross-connected to twoends of the input Vin, that is, the first input voltage end Vbus+ andthe second input voltage end Vbus− and used to reduce the equivalentloop inductance of the bridge in the converter. Referring to FIG. 4 band FIG. 4 c, FIG. 4 b is a schematic cross-sectional view showing apower module 400 a according to the power module 400 of FIG. 4 a, andFIG. 4 c is a schematic top view showing the power module 400 aaccording to FIG. 4 b. As shown in FIGS. 4 b and 4 c, theheat-dissipating substrate 23 and the pin 24 in the power module 400 aare disposed on a circuit board 29 by soldering or bonding. In thisembodiment, the heat-dissipating substrate 23 and the pin 24 aresoldered onto the circuit board 29 through solder 25, but thisembodiment is not limited to this connection method. It should beexplained that the circuit board can be a print circuit board (PCB) orcan be another circuit board capable of carrying electronic elements.

In addition, the capacitor C can be disposed on the upper surface or thelower surface of the circuit board 29 (in this embodiment, the capacitorC is disposed on the upper surface of the circuit board 29) and isconnected between the heat-dissipating substrate 23 and the first inputvoltage pin Vbus+ through solder 25 (e.g. soldering). Theheat-dissipating substrate 23 is also connected to the second inputvoltage end Vbus− (not shown in the FIG. 4 c), that is, theheat-dissipating substrate 23 and the second input voltage end Vbus− areequipotential. Moreover, the capacitor C of the present embodiment isdisposed near the first planar power device 21 and the second planarpower device 22, such that the equivalent loop inductance formed by thecapacitor C and the bridge is quite small, which generally can bereduced from several tens of nano-henries (nH) to teens of nano-henries,thus benefiting the operation of the power module 400 a under highfrequency.

In order to reduce the loop inductance, referring to FIG. 4 d and FIG. 4e, FIG. 4 d is a schematic cross-sectional view showing another powermodule 400 b according to the power module 400 of FIG. 4 a, and FIG. 4 eis a schematic top view showing the power module 400 b according to FIG.4 d. As shown in FIG. 4 d and FIG. 4 e, the capacitor C is furtherdirectly disposed on the heat-dissipating substrate 23 and the firstinput voltage pin Vbus+, and the capacitor C is soldered onto theheat-dissipating substrate 23 and the first input voltage pin Vbus+through solder 25. Moreover, in the present embodiment, the position ofthe capacitor C disposed on the first input voltage end Vbus+ and thesecond input voltage end Vbus− of the half-bridge converter is muchnearer the first planar power device 21 and the second planar powerdevice 22, compared to the position of the capacitor C disposed on thepower module 400 a in FIG. 4 a and FIG. 4 b. Therefore, its loopinductance can further be reduced to be generally less than tennano-henries.

Although the equivalent inductance of the power module 400 b has beengreatly improved. However, a GaN device is usually constructed by tensof thousands of GaN cells, and the loop sizes formed by each area of theGaN device and the capacitor C (as shown in FIG. 4 d) are different fromeach other, which may easily result in the inconsistent switching speedof each GaN cell in the switching process and affects the performance ofthe power module 400 b. Hence, in the packaging design, not only toreduce the loop inductance of the power module, but also how to equallydistribute each loop should be considered.

Referring to FIG. 4 f and FIG. 4 g, FIG. 4 f is a schematiccross-sectional view showing another power module 400 c according to thepower module 400 of FIG. 4 a. FIG. 4 g is a schematic top view showingthe power module 400 c according to FIG. 4 f. As shown in FIG. 4 f andFIG. 4 g, the capacitor C is directly disposed on the upper surface ofthe first planar power device 21 and the upper surface of the secondplanar power device 22. One end of the capacitor C is directly connectedto the drain D₁ of the first planar power device 21, and the other endof the capacitor C is directly connected to the source S₂ of the secondplanar power device 22. Thus, not only the loop inductance is reduced,but also the uniformity of the circuit is also ensured. In thisembodiment, the equivalent loop inductance of the power module 400 c canbe further reduced less than one nano-henry.

Referring to FIG. 4 h, FIG. 4 h is a schematic cross-sectional viewshowing another power module 400 d according to the power module 400 ofFIG. 4 a. As shown in FIG. 4 h, the first planar power device 21 and thesecond planar power device 22 of the power module 400 d are disposed onthe same chip, that is, the two planar power devices are not divided ina wafer. In this embodiment, the adjacent first/second planar powerdevices 21 and 22 are directly disposed on the heat-dissipatingsubstrate 23, and the capacitor C is directly disposed on the uppersurface of the first planar power device 21 and the upper surface of thesecond planar power device 22, similar to the capacitor disposition ofthe power module 400 c in the FIG. 4 f. One end of the capacitor C isdirectly connected to the drain D₁ of the first planar power device 21,and the other end of the capacitor C is directly connected to the sourceS₂ of the second planar power device 22.

In the same chip, because two adjacent planar GaN power devices stillhave electrical insulation features, the two adjacent planar GaN powerdevices are cut together and not divided during wafer cutting, that is,the two planar GaN power devices are disposed on the same chip and arespaced from each other at a smallest distance, as shown in FIG. 4 h.Therefore, the space availability of the power module 400 d can beimproved, and the current may evenly flow in the smallest loop via thestacking of the capacitor C, thereby greatly improving the equivalentloop inductance.

The GaN device is generally a normally-on device, meaning that thenormally-on device is conducted (on) when no control signal is provided.It also represents that, when the power module is under a standby mode,a current through each device of the power module is likely to begenerated. If the unexpected current through a device is too large, thedevice in the power module may be further damaged. Hence, in order toensure the power module using the normally-on device to be more stable,the normally-on device is usually used with a conventional switchingdevice (i.e. a normally-off device). That is, the normally-off device isopen (off) when no control signal is provided, thereby enhancing thestability of the operation of the power module.

Referring to FIG. 5 a, FIG. 5 a shows a circuit diagram of a half-bridgeconverter according to an embodiment of the present invention. As shownin FIG. 5 a, a power module 500 a in the half-bridge converter includesthe first planar power device 21, the second planar power device 22, anda switching device 50. The drain D₃ of the switching device 50 isconnected to one end of the input Vin, and the source S₃ is connected tothe drain D₁ of the first planar power device 21. The drain S₁ of thefirst planar power device 21 is connected to the drain D₂ of the secondplanar power device 22, and the source S₂ of the second planar powerdevice 22 is connected to the other end of the input source Vin (thatis, a ground end). The source S₁ of the first planar power device 21 andthe drain D₂ of the second planar power device 22 are connected to theoutput end Vo.

In this embodiment, at least one of the first planar power device 21 andthe second planar power device 22 is a normally-on GaN device. In thisembodiment, the first planar power device 21 and the second planar powerdevice 22 are both normally-on devices, but this embodiment is notlimited thereto. The switching device 50 is a normally-off device,generally such as a metal-oxide-semiconductor field-effect transistor(SiMOS, referred to as a silicon device). It is noted that GaN devicecan also be implemented as a normally-off device, meaning that theswitching device 50 can also be a normally-off GaN device. If notspecifically described in the following embodiments, the normally-offdevices are regarded as commonly seen silicon devices.

The first planar power device 21, the second planar power device 22, andthe switching device 50 are all high voltage devices, that is, the firstplanar power device 21, the second planar power device 22 and theswitching device 50 can independently resist the high voltage inputsource Vin. While the first planar power device 21 and the second planarpower device 22 are not under a working mode, the switching device 50 iscontrolled at an off state to prevent high flowing current from damagingthe devices when the first planar power device 21 and the second planarpower device 22 are in an on state. While the first planar power device21 and the second planar power device 22 are conducted (on), theswitching device 50 is controlled at the on state to lower the powerconsumption of the power module 500 a. Moreover, the first planar powerdevice 21 and the second planar power device 22 are operated at arelatively high frequency, and the switching device is operated at arelatively low frequency.

Referring to FIG. 5 b, FIG. 5 b shows a circuit diagram of a powermodule 500 b according to an embodiment of the present invention. Asshown in FIG. 5 b, the power module 500 b includes a first planar powerdevice 51, a second planar power device 52, a first switching device 53,a second switching device 54 and a capacitor C. Similarly, the firstplanar power device 51 and the second planar power device 52 are bothnormally-on GaN devices, and the first switching device 53 and thesecond switching device 54 are normally-off silicon device (e.g. ametal-oxide-semiconductor field-effect transistor, SiMOS). The source S₁of the first planar power device 51 is connected the drain D₃ of thefirst switching device 53 in series. The source S₃ of the firstswitching device 53 is connected to the drain D₂ of the second planarpower device 52 in series. The source S₂ of the second planar powerdevice 52 is connected to the drain D₄ of the second switching device 54in series. The drain D₁ of the first planar power device 51 is connectedto the first input voltage end Vbus+. The source S₄ of the secondswitching device 54 is connected to the second input voltage end Vbus−.One end of the capacitor C is connected to the first input voltage endVbus+, and the other end is connected to the second input voltage endVbus− (that is, a ground end). The source of the first switching device53 is connected to the drain of the second planar power device 52 andthe output end Vo.

Because the first switching device 53 and the second switching device 54are respectively connected to the source S₁ of the first planar powerdevice 51 and the source S₂ of the second planar power device 52 inseries, their working voltage is relatively low (which is the maximumgate voltage of the GaN device, generally lower than 20 volts), and thefirst switching device 53 and the second switching device 54 are bothlow voltage devices unlike the power module 500 a, so as to furtherreduce the power consumption of the power module 500 b.

Moreover, the first/second planar power devices 51, 52 in the powermodule 500 b and the first/second switching device 53, 54 can beoperated in two modes. The first mode is that the first/second planarpower devices 51, 52 and the first/second switching devices 53, 54 areoperated in a high frequency mode concurrently. Accordingly, the firstplanar power device 51 and the second planar power device 52 can becontrolled by directly controlling the first switching device 53 and thesecond switching device 54. The second mode is that the first/secondplanar power device 51, 52 are operated in the high frequency mode, butthe first/second switching devices 53, 54 are operated in a lowfrequency mode, like the working mode of the power module 500 a. In thesecond mode, the first/second switching device 53, 54 are controlled inthe off state when the first/second planar power device 51, 52 are notin the working state, and the first/second switching device 53, 54 arecontrolled in the on-state when the first/second planar power device 51,52 are in the normal working state, so as to lower the loss. However,this controlling method is relatively complicated.

Referring to FIG. 6, FIG. 6 shows a circuit diagram of a power module600 according to an embodiment of the present invention. As shown inFIG. 6, the power module 600 includes a first planar power device 61, asecond planar power device 62, a switching device 63, a first capacitorC1 and a second capacitor C2. The first planar power device 61, thesecond planar power device 62 and the switching device 63 are connectedin series. The first capacitor C1 is electrically connected to the drainD₁ of the first planar power device 61 and the source S₃ of theswitching device 63. The second capacitor C2 is electrically connectedto the drain D₁ of the first planar power device 61 and the source S₂ ofthe second planar power device 62.

Similarly, at least one of the first planar power device 61 and thesecond planar power device 62 is the normally-on GaN device, and theswitching device 63 is the normally-off silicon device. In addition, thefirst planar power device 61 and the second planar power device 62 arehigh voltage devices, and their voltage withstand capacities areapproximately the same and are two times greater than the voltagewithstand capacity of the switching device 63. Because the first/secondplanar power devices 61, 62 are high voltage devices, which canindependently resist the input voltage, only one switching device 63 isneeded to help the planar power devices keep under the off state whenthe first/second planar power devices 61, 62 are not operated yet.

When the switching device 63 is operated under the low frequency mode,the loop inductance can be lowered by integrating the second capacitorC2. When the switching device 63 is operated under the high frequencymode, the loop inductance can be lowered by integrating the firstcapacitor C1. However, compared to the power module 500 b in FIG. 5 b,the loop of the power module 600 is involved in fewer devices (onenormally-off silicon device less), hence its equivalent loop inductancecan be reduced by 20% or more, which is beneficial for the power moduleoperated under high frequency.

It is noted that, from FIG. 5 a to FIG. 6, the packaging process of eachpower module includes at least two normally-on GaN chips with at leastone normally-on silicon chip to form a bridge of the converter. By usinga combination of chips to implement a functional device, the combinationcan be regarded as a device, as shown in FIG. 7. FIG. 7 shows a circuitdiagram of a switching device 700 according to an embodiment of thepresent invention, in which the switching device 700 is implemented by acombination of a high voltage normally-on GaN chip 71 and a low voltagenormally-off silicon chip 72. Although the switching device 700 includestwo different devices, but the equivalent function of the switchingdevice 700 is still the normally-off device, and hence still can be usedas a device.

Referring to FIG. 6, FIG. 8 a and FIG. 8 b, FIG. 8 a is a schematiccross-sectional view of a power module 800 a according to the circuitdiagram of FIG. 6, and FIG. 8 b is a top view showing a power module 800a according to FIG. 8 a. It should be noted that, in this embodiment,the switching device 63 a is also a planar device. Accordingly, in FIG.8 a and FIG. 8 b, the first planar power device 61, the second planarpower device 62 and the switching device 63 a are respectively inparallel and directly disposed on the heat-dissipating substrate 23. Thedrain D₃ of the switching device 63 a is connected to the source S₂ ofthe second planar power device 62. The drain S₃ of the switching device63 a is connected to the heat-dissipating substrate 23, and meanwhilethe heat-dissipating substrate 23 is used as the second input voltagepin Vbus− (not shown in FIG. 8 a and FIG. 8 b), in which the electricpotential is the potential of the second voltage input end Vbus−. Thedrain D₂ of the second planar power device 62 is connected to the sourceS₁ of the first planar power device 61, and each electrode in the eachdevice is connected to the corresponding pin 24, in which theirconnections can be accomplished though wire bonding.

In addition, the power module 800 a further includes a circuit board 29,and the heat-dissipating substrate 23 and the pin 24 are disposed on thecircuit board 29. It is noted that, the capacitor C1 and C2 of the powermodule 800 a can be disposed by any method described in theaforementioned embodiments, and this embodiment is not limited thereto.In this embodiment, the first capacitor C1 is disposed on the circuitboard 29. It is noted that, the capacitor Cl can be disposed on theupper surface or lower surface of the circuit board 29. In thisembodiment, the capacitor C1 is disposed on the upper surface of thecircuit board 29, but is not limited thereto. In addition, one end ofthe first capacitor C1 is connected to the heat-dissipating substrate 23through the solder 25, and the other end thereof is connected to thefirst input voltage pin Vbus+ through the solder 25, and the firstcapacitor C1 is disposed near the first planar power device 21 and thesecond planar power device 22. The second capacitor C2 is disposed onthe upper surface of the first planar power device 61 and the uppersurface of the second planar power device 62, and is directly connectedto the drain D₁ of the first planar power device 61 and the source S₂ ofthe second planar power device 62 respectively.

In the circuit of FIG. 6, the switching device 63 is located at the lowvoltage end, and hence, in FIG. 8 a one of two power electrodes (thatis, the source S₃ and the drain D₃) of the switching device 63 a can beconnected to the heat-dissipating substrate 23 to reduce the influenceof electromagnetic interference. Besides, there is no other normally-offsilicon device disposed on the high voltage position in the power module600, and thus, the bottom of the switching device 63 a in the powermodule 800 a will not have the problems of insufficient voltagewithstand capacity (because the switching device 63 a is the low voltagedevice).

Referring to FIG. 8 c, FIG. 8 c is a schematic cross-sectional view of apower module 800 b according to a circuit diagram of FIG. 6. In thisembodiment, a vertical-type device (like vertical-type Si MOS) isapplied to the switching device 63 b, meaning that not all electrodes ofthe vertical-type device are disposed on the same plane. In thisembodiment, the gate G₃ and the source S₃ of the switching device 63 bare located on the upper surface of the switching device 63 b, and thedrain D₃ is located at the bottom of the switching device 63 b. As shownin FIG. 8 c, while the switching device 63 b is directly disposed on theheat-dissipating substrate 23, the electric potential of theheat-dissipating substrate 23 connected to the drain D₃ is equivalent tothe electric potential Vp in the circuit diagram shown in FIG. 6 becausethe bottom of the switching device is the drain D₃. In FIG. 6, thevoltage of the switching device 63 is relatively low, and thus, when thepower module 600 is operated, the switching device 63 is generallyconducted, and its potential Vp can be regarded as a relatively stablepotential, and hence the influence of the electromagnetic interferencecan be ignored. In addition, the potential of the heat-dissipatingsubstrate 23 in the power module 800 b is configured at the potentialVp, and the first planar power device 61, the second planar power device62 and the switching device 63 b are disposed in parallel directly onthe heat-dissipating substrate 23, and the source of the second planarpower device 22 is connected to the heat-dissipating substrate 23,thereby the loop length of the power module 800 b is efficiently reducedso as to lower its equivalent loop inductance. Furthermore, the pins 24also include another output voltage pin (not shown in FIG. 8 b), inwhich the source of the second planar power device 62 is electricallyconnected to another output voltage pin for providing another outputvoltage end to the power module 800 b.

In this embodiment, only the arrangement method of the second capacitorC2 is shown, and the first capacitor C1 (not shown in FIG. 8 b) can bedisposed by any arrangement method described in the aforementionedembodiments, which will not be repeated herein. In this embodiment, thesecond capacitor C2 is disposed on the upper surface of theheat-dissipating substrate 23 and the pin 24 (i.e. the first inputvoltage pin Vbus+), but the embodiment is not limited thereto.

Because the switching device paired with GaN power device is generally asilicon power device, and the silicon power device is generally a lowvoltage device, the voltage withstand capacity between its substrate andelectrodes cannot match with that of the GaN power device. Hence, aportion of the switching devices can be separately mounted. Because theswitching devices are merely disposed for collaborating with theswitching control of the GaN power device, and the loss thereof isrelatively small, the heat dissipating requirement does not need to beconsidered. Referring to FIG. 8 d, FIG. 8 d is a schematiccross-sectional view of a power module 800 c according to a circuitdiagram of FIG. 6. As shown in FIG. 8 d, the drain D₃ of the switchingdevice 63 b is directly connected to the source S₂ of the second planarpower device 62, thereby utilizing space effectively. In addition, inFIG. 8 d, the first capacitor C1 and the second capacitor C2 are notshown in the power module 800 c, but the first capacitor C1 and thesecond capacitor C2 can be disposed by any arrangement method describedin the aforementioned embodiments, and are not illustrated again herein.

Referring to FIG. 9, FIG. 9 is a schematic cross-sectional view showinga power module 900 according to an embodiment of the present invention.The power module 900 also includes at least one planar device 91. Forconvenience and clarity of explanation, in FIG. 9 only a planar device91 is shown, but the embodiment is not limited thereto. The planardevice 91 can be a control chip or a drive chip. In order to performbetter driving performance and improve space availability, the planardevice 91 (controlling device/driving device) can also be disposed inparallel with the first planar power device 21, the second planar powerdevice 22 and directly on the heat-dissipating substrate 23.Accordingly, the driving performance of the power module 900 can bebetter. For example the driving speed can be improved from theconventional speed of tens of nano-seconds (nS) to teens of nano-secondseven to single-digit nano-seconds.

In the practical application, if in the packaging process, more devices,like a driving device, a current sensor and a temperature sensor (e.g.negative temperature coefficient, NTC) are desired to be integrated inthe power module, then these devices can be disposed on an insulatinglayer, which can be a print circuit board (PCB). Moreover, there is aconductive circuit layer covering the insulating layer to help theinternal connections of the devices.

Referring to FIG. 10 a and FIG. 10 b, FIG. 10 a is a schematiccross-sectional view showing a power module 110 a according to anembodiment of the present invention, and FIG. 10 b is a schematic topview showing a power module 110 a according to FIG. 10 a. The powermodule 110 a includes the first planar power device 21, the secondplanar power device 22, the heat-dissipating substrate 23, a switchingdevice 63 b, a controlling device IC1, a driving device IC2, a capacitorC, a plurality of pins 24, and an insulating layer 111. The controllingdevice IC1 and the driving device IC2 are both planar devices. In thisembodiment, the number of each of the first planar power device 21, thesecond planar power device 22, the switching device 63 b, the drivingdevice IC1 and the driving device IC2 is one, but this embodiment is notlimited thereto.

In this embodiment, the power module 110 a includes two planar deviceswhich are the controlling device 101 and the driving device IC2. Asshown in FIG. 10 a and FIG. 10 b, because the switching device 63 b, thecontrolling device 101, the driving device IC2 and the capacitor C donot demand a lot of heat dissipation, they can be directly disposed onthe insulating layer 111. The insulating layer 111 can be a PCB which atleast contains two layers of boards. The insulating layer 111 is coveredwith a conductive circuit layer to help the internal connections of thedevices. In addition, the insulating layer 111 can be directly solderedon the heat-dissipating substrate 23 for convenience, and several viascan be disposed on the insulating layer 111 for transmitting the heat onthe heat-dissipating substrate 23 to the upper surface of the insulatinglayer 111, thereby achieving the effects of double-sides heatdissipation. It is noted that, because the devices disposed on theinsulating layer 111 do not demand a lot of heat dissipation, cheapmaterials (e.g. circuit board) rather than expensive materials (e.g.directed bonded copper, DBC) can be used for forming the insulatinglayer 111 to reduce the cost of manufacturing the power module 110 a.

Further, for reducing the equivalent loop inductance of the powermodule, the arrangement of the capacitor still has great importance.Referring to FIG. 10 c and FIG. 10 d, FIG. 10 c is a schematiccross-sectional view showing a power module 110 b according to anembodiment of the present invention, and FIG. 10 d is a schematic topview showing a power module 110 b according to FIG. 10 c. In thisembodiment, the capacitor C of the power module 110 b is disposed on theupper surface of the first planar power device 21 and the upper surfaceof the second planar power device 22, and is directly connected to thedrain D₁ of the first planar power device 21 and the source S₂ of thesecond planar power device 22 by soldering so as to get a minimumequivalent loop inductance, but the arrangement of the capacitor C isnot limited to this embodiment. Hence, the electrical property of thepower module 110 b is greatly improved without affecting otherproperties.

In the aforementioned embodiments, after completing the connections ofthe respective devices (e.g. by wire bonding), all areas of the devicesare covered by a molding material 27 by molding, injecting, so as toprotect the devices. For example, the molding material 27 is formed tocover the first planar power device 21 and the second planar powerdevice 22; or the molding material 27 is formed to cover the controllingdevice 101, the driving device IC2, the capacitor C, and the switchdevice 63 b; or the molding material 27 is formed to cover a portion ofthe controlling device IC1, the driving device IC2, the capacitor C, theswitch device 63 b, the insulating layer 111, the heat-dissipatingsubstrate 23 and the pins 24. However, with the use of the insulatinglayer, the molding process of the power module does not need to coverall the area, but only need to cover a portion of the devices. Referringto FIG. 10 e and FIG. 10 f, FIG. 10 e is a schematic cross-sectionalview showing a power module 110 c according to an embodiment of thepresent invention, and FIG. 10 f is a schematic top view showing a powermodule 110 c according to FIG. 10 e. As shown in FIG. 10 e and FIG. 10f, the molding material 27 merely covers a portion area of the powermodule 110 c. For example, the molding material 27 merely covers thefirst planar power device 21 and the second planar power device 22, andthe other uncovered portions can be protected by the insulating layer111 to achieve the dustproof, moisture-proof, electrical insulationfunctions. Thus, the fabrication cost of the power module is furtherdecreased, the space occupied by the power module is reduced and alsothe heat dissipating performance of the power module is improved.

It is noted that, in the aforementioned embodiment, the pin 24 and theheat-dissipating substrate 23 are both disposed on the same plane, thatis, the pin 24 and the heat-dissipating substrate 23 are located in thesame side of the insulating layer 111. However, the pin 24 and theheat-dissipating substrate 23 may also be disposed on differentsurfaces, that is, the pin 24 and the heat-dissipating substrate 23 arelocated in different sides of the insulating layer 111 to increase thearea of the heat-dissipating substrate 23, as shown in FIG. 10 g. FIG.10 g is a schematic cross-sectional view showing a power module 110 daccording to an embodiment of the present invention. In this embodiment,the pin 24 is disposed on the insulating layer 111, and on the differentplane from the heat-dissipating substrate 23. Each device of the powermodule 110 d is connected to the pin 24 through the bonding wire 26 andthe electro-conductive circuit layer of the insulating layer 111 (notshown in FIG. 10 g). Thus, the area of the heat-dissipating substrate 23can be enlarged to improve the heat dissipating performance of the powermodule 110 d.

Similarly, the power module 110 d may be partially molded. Referring toFIG. 10 h, FIG. 10 h is a schematic cross-sectional view showing a powermodule 110 e according to an embodiment of the present invention. Asshown in FIG. 10 h, the pin 24 of the power module 110 e is alsodisposed on the insulating layer 111, and the molding material 27 coversonly a portion of the power module 110 e. For example, the moldingmaterial 27 covers the first planar power device 21 and the secondplanar power device 22. Thus, the heat dissipating performance of thepower module can be further improved (because the area of theheat-dissipating substrate 23 is also increased), and also thefabrication cost of the power module and the space occupied thereby canbe reduced.

Except for the advantages described above, the arrangement of the pin 24and the heat-dissipating substrate 23 disposed on the different planesmay facilitate the disposition of another heat sink as shown in FIG. 10i. FIG. 10 i is a schematic cross-sectional view showing a power module110 f according to an embodiment of the present invention. The powermodule further includes a heat sink 112 disposed on another side of theheat-dissipating substrate 23 to satisfy the requirement of the powermodule with larger power.

Referring to FIG. 11, FIG. 11 is a schematic diagram showing a powerconverter 210 according to an embodiment of the present invention. Asshown in FIG. 11, the power converter includes a power module 211, apower input terminal VI, a power output terminal VO, and a heat sink212. The power module 211 can be any one of the power modules in theaforementioned embodiment, but is not limited thereto. The power inputterminal VI and the power output terminal VO are connected to the powermodule 211. The heat sink 212 can be disposed adjacent to theheat-dissipating substrate (not shown in FIG. 11) in the power module211 in order to provide better heat dissipating performance to the powerconverter 210.

Moreover, the power converter 210 receives an input voltage through thepower input terminal VI, and the input voltage is converted into anoutput voltage through the power converter 211. Then, the aforementionedoutput voltage is outputted through the power output terminal VO toachieve electric power conversion. According to the classifications ofthe electric power conversion, the power converters may be classifiedinto any one of a non-isolated AC/DC power converter, a non-isolatedDC/DC power converter, an isolated DC/DC converter, and an isolatedAC/DC power converter. Accordingly, the power module 211 can be changedin the power converter 210 of the embodiment of the present invention toachieve the function of the electric power conversion.

Referring to FIG. 12 a, FIG. 12 a is a schematic diagram showing a powerconverter 310 a according to an embodiment of the present invention. Asshown in FIG. 12 a, the power converter 310 a includes the power module211, the heat sink 212, a pin 311, a circuit board 312, a firstintegrated device 313, a second integrated device 314 and a shell 315.The heat sink 212 can be disposed or integrated adjacent to theheat-dissipating substrate (not shown in FIG. 12 a) in the power module211, and the power module 211 is connected to the circuit board 312though the pin 311. Also, the power converter 310 a includes the firstintegrated device 313 and the second integrated device 314 to provideother functions required by the power converter 310 a. It is noted that,because several vias (not shown in FIG. 12 a) are disposed on theinsulating layer of the power module 211, the power module 211 candissipate heat from its two sides (double-sides heat dissipation).Hence, when the power module 211 is disposed, the two sides of the powermodule 211 should have air channels, as shown in the area a1 and a2 inFIG. 12 a, so as to enable the power module 211 to have the best heatdissipating performance.

Referring to FIG. 12 b, FIG. 12 b is a schematic diagram showing a powerconverter 310 b according to an embodiment of the present invention. Asshown in FIG. 12 b, one side of the power module 211 of the powerconverter 310 b is assembled onto the shell 315, and another sidethereof provides an air channel (area b1) to implement the double sidesheat dissipation for the power module 211.

Referring to FIGS. 13 a to 13 f, FIGS. 13 a to 13 f are schematicdiagrams showing processes of manufacturing power modules according toan embodiment of the present invention. First, as shown in FIG. 13 a, aheat-dissipating substrate 23 is provided which can be formed from agood electro-conductive and thermo-conductive material, such as copper,aluminum and graphite or the like. Then, the position of the powerdevice to be disposed on the heat-dissipating substrate 23 is planed,and solder or an adhesive agent is attached to the heat-dissipatingsubstrate 23 by coating, dispensing or the like. In this embodiment, thesolder 25 is attached to the heat-dissipating substrate 23, but theattachment method is not limited thereto.

Next, as shown in FIG. 13 b, at least one first planar power device 21and a second planar power device 22 are provided, and the first planarpower device 21 and the second planar power device 22 are disposed on aplanned position on the heat-dissipating substrate 23 by soldering,adhering or the like. In this embodiment, the first planar power device21 and the second planar power device 22 are disposed on theheat-dissipating substrate 23 by soldering, but the embodiment is notlimited to soldering.

Then, as shown in FIG. 13 c, a insulating layer 111 is provided, and therelated devices include at least one planar device 91 (e.g. acontrolling device IC1 or a driving device IC2), at least one switchingdevice 63 b, at least one capacitor C, and the pin 24 are disposed onthe insulating layer 111. For convenience and clarity of explanation,the number of each of the planar device 91, the switching device 63 b,the capacitor C and the pin 24 shown in the embodiment is one, but thisembodiment is not limited thereto. Moreover, in this embodiment, thesurface mount devices (SMD) reflow technique is applied to mount theplanar device, the switching device 63 b, the capacitor C and the pin 24on the insulating layer 111, but this embodiment is not limited thismounting method. Moreover, the insulating layer 111 can be a circuitboard, which is formed from electrically insulating materials, and theinsulating layer 111 is covered with an electro-conductive circuit layer(not shown in FIG. 13 c) to help the internal connections of devicesmounted on the insulating layer 111. Then, the insulating layer 111covers the heat-dissipating substrate 23, and covers the first planarpower device 21 and the second planar power device 22.

Then, as shown in FIG. 13 d, the first planar power device 21, thesecond planar power device 22, the planar device 91, the switchingdevice 63 b, and the capacitor C are connected to the corresponding pins24 by wire bonding, lithography, soldering or the like. In thisembodiment, the connection method is wire bonding, and each device isconnected to the corresponding position through wire bonding 26, butthus embodiment is not limited to this connection method.

Thereafter, as shown in FIG. 13 e, the insulating layer 111 is formed tocover the molding material 27 by dispensing, molding technique or thelike, such that the modeling material can uniformly cover the planardevice 91, the switching device 63 b, the capacitor C and a portion ofthe pin 24, so that the mechanical, dustproof, moisture-proof, andinsulation protection functions may be achieved. Then, as shown in FIG.13 f, another heat sink 212 can be disposed adjacently to another sideof the heat-dissipating substrate 23, thereby increasing the heatdissipating performance of the power module.

In a process diagram of manufacturing a power module provided in oneembodiment of the present invention, the arrangement positions of theplanar device 91, the switching device 63 b, the capacitor C and the pin24 can be any positions disclosed in the aforementioned embodiments.This embodiment merely uses one of the aforementioned embodiments as anexample, but this embodiment is not limited thereto.

In the aforementioned embodiments, the packaging method of the powermodule uses the implementation of the half-bridge circuit as an example,that is, at least two of planar GaN power devices are used to implementthe structure of the half-bridge. However, the packaging method of thepower device in the aforementioned embodiments can also be applied tothe integrated circuit having more bridges or to a non-bridge circuit.

Referring to FIG. 14, FIG. 14 shows a half-bridge circuit 410 accordingto an embodiment of the present invention. As shown in FIG. 14, thesource S₁ of a first planar GaN power device 411 is connected to asource S₂ of the second planar GaN power device 422. In addition, thedrain D₁ of the first planar GaN power device 411 and the drain D₂ ofthe second planar GaN power device 422 are respectively connected to afirst input voltage terminal Vin1 and a second input voltage terminalVin2. In other words, the first planar GaN power device 411 and thesecond planar GaN power device 412 are respectively constructed by theupper and lower bridge arms of the half-bridge circuit 410 to implementthe function of rectification.

As known in the aforementioned embodiment of the present invention, notonly the space availability is effectively increased, but also the costof disposing the DCB ceramic substrate is saved via the power moduleformed by directly disposing the planar power device on theheat-dissipating substrate. Moreover, the heat dissipating performanceof the power module can be significantly enhanced, and the electricproperty of the power module is improved as well by the capacitordisposition. Thus, high efficiency or high power density of the powerconverter can also be achieved, and the energy conversion efficiency ofthe power converter can also be advantageously enhanced.

Although the present invention has been described in considerable detailwith reference to certain embodiments thereof, other embodiments arepossible. Therefore, the spirit and scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims.

What is claimed is:
 1. A power module, comprising: a heat-dissipatingsubstrate; a first planar power device comprising a plurality ofelectrodes which are all on an upper surface of the first planar powerdevice; and a second planar power device comprising a plurality ofelectrodes which are all on an upper surface of the second planar powerdevice; wherein a lower surface of the first planar power device and alower surface of the second planar power device are disposed above theheat-dissipating substrate.
 2. The power module of claim 1, wherein theheat-dissipating substrate is made from an electro- andthermo-conductive material.
 3. The power module of claim 2, wherein atleast one of the first planar power device and the second planar powerdevice is a gallium-nitride (GaN) power device.
 4. The power module ofclaim 2, further comprising a electrically insulating thermallyconductive layer disposed between the lower surface of the first planarpower device and the heat-dissipating substrate, wherein the lowersurface of the second planar power device is disposed on theheat-dissipating substrate.
 5. The power module of claim 2, furthercomprising at least one planar device, wherein the at least one planardevice and the first planar power device, and the second planar powerdevice are disposed in parallel on the heat-dissipating substrate. 6.The power module of claim 5, wherein the at least one planar device is adrive chip or a control chip.
 7. The power module of claim 2, furthercomprising a vertical-type power device, wherein the vertical-type powerdevice is directly disposed on the electrodes of the first planar powerdevice or the electrodes of the second planar power device, or thevertical-type power device, the first planar power device and the secondplanar power device are disposed in parallel on the heat-dissipatingsubstrate.
 8. The power module of claim 2, further comprising aplurality of pins, wherein the electrodes of the first planar powerdevice and the electrodes of the second planar power device areconnected to the corresponding pins, respectively.
 9. The power moduleof claim 8, wherein the pins comprise an input voltage pin and at leastone output voltage pin, and the electrodes of the first planar powerdevice comprises a drain electrically connected with the input voltagepin and a source electrically connected with the at least one outputvoltage pin, and the electrodes of the second planar power devicecomprise a drain electrically connected with the at least one outputvoltage pin and a source electrically connected to the heat-dissipatingsubstrate.
 10. The power module of claim 9, further comprising acapacitor, wherein one end of the capacitor is directly connected to theheat-dissipating substrate, and the other end of the capacitor isdirectly connected to the input voltage pin.
 11. The power module ofclaim 9, further comprising a capacitor disposed on the upper surface ofthe first planar power device and the upper surface of the second planarpower device, wherein one end of the capacitor is directly connected tothe drain of the first planar power device, and the other end of thecapacitor is directly connected to the source of the second planar powerdevice.
 12. The power module of claim 11, wherein the first planar powerdevice and the second planar power device are disposed on the same chip.13. The power module of claim 9, further comprising: a capacitor; and acircuit board; wherein the capacitor, the heat-dissipating substrate andthe pins are disposed on the circuit board, and one end of the capacitoris connected to the heat-dissipating substrate, and the other end of thecapacitor is electrically connected to the input voltage pin.
 14. Thepower module of claim 8, further comprising at least one switchingdevice, wherein the at least one switching device is electricallyconnected to the electrodes of the first planar power device or theelectrodes of the second planar power device.
 15. The power module ofclaim 14, wherein at least one of the first planar power device and thesecond planar power device is a normally-on device and the at least oneswitching device is a normally-off device.
 16. The power module of claim15, wherein the at least one switching device is a normally-off silicon(Si) device or a normally-off gallium-nitride (GaN) device.
 17. Thepower module of claim 14, wherein the voltage withstand capacity of thefirst planar power device is substantially the same as the voltagewithstand capacity of the second planar power device, and the voltagewithstand capacity of the first planar power device is at least twotimes greater than the voltage withstand capacity of the at least oneswitching device.
 18. The power module of claim 14, wherein the at leastone switching device comprises: a first switching device of which oneend is electrically connected to a source of the first planar powerdevice and the other end is electrically connected to a drain of thesecond planar power device; and a second switching device of which oneend is electrically connected to a source of the second planar powerdevice and the other end is electrically connected to a ground terminal.19. The power module of claim 14, wherein the at least one switchingdevice comprises a switching device having a first end and a second end,and the first end is electrically coupled with a source of the secondplanar power device, the power module further comprising: a firstcapacitor of which one end is electrically coupled with a drain of thefirst planar power device and the other end is electrically coupled witha source of the second planar power device.
 20. The power module ofclaim 19, wherein the voltage withstand capacity of the first planarpower device and the voltage withstand capacity of the second planarpower device, are at least two times greater than the voltage withstandcapacity of the switching device.
 21. The power module of claim 19,wherein the first planar power device and the second planar power deviceare both normally-on devices.
 22. The power module of claim 19, furthercomprising: a second capacitor of which one end is electrically coupledwith a drain of the first planar power device and the other end iselectrically coupled with the second end of the switching device; and acircuit board on which the first capacitor, the heat-dissipatingsubstrate, and the pins are disposed, wherein the first capacitor isadjacent to the first planar power device and the second planar powerdevice.
 23. The power module of claim 19, wherein the second capacitoris disposed on the upper surface of the first planar power device andthe upper surface of the second planar power device.
 24. The powermodule of claim 19, wherein the pins comprise a first input voltage pin,and the first capacitor is disposed on the first input voltage pin andthe heat-dissipating substrate.
 25. The power module of claim 19, thepins comprising: a first input voltage pin to which the drain of thefirst planar power device is electrically connected; and a second inputvoltage pin to which the second end of the switching device iselectrically connected; wherein the source of the second planar powerdevice is electrically connected to the heat-dissipating substrate. 26.The power module of claim 19, wherein the switching device, the firstplanar power device, and the second planar power device are disposedside by side and directly on the heat-dissipating substrate.
 27. Thepower module of claim 19, wherein the switching device is disposed onthe upper surface of the first planar power device or on the uppersurface of the second planar power device.
 28. The power module of claim8, further comprising at least one planar device, at least one firstcapacitor, and an insulating layer, wherein the at least one planardevice and the at least one first capacitor are disposed on theinsulating layer, and the insulating layer is disposed on theheat-dissipating substrate.
 29. The power module of claim 28, furthercomprising a second capacitor, wherein the second capacitor is disposedon the upper surface of the first planar power device and on the uppersurface of the second planar power device.
 30. The power module of claim28, further comprising at least one switching device, wherein the atleast one switching device is disposed on the insulating layer, and theheat-dissipating substrate and the pins are disposed on the same side ofthe insulating layer.
 31. The power module of claim 28, furthercomprising at least one switching device, wherein the at least oneswitching device is disposed on the insulating layer, and theheat-dissipating substrate and the pins are disposed on two sides of theinsulating layer respectively.
 32. The power module of claim 30,comprising a molding material covering the first planar power device andthe second planar power device.
 33. The power module of claim 31,comprising a molding material covering the first planar power device andthe second planar power device.
 34. The power module of claim 32,wherein the molding material further covers the at least one planardevice, the at least one switching device and the at least one firstcapacitor.
 35. The power module of claim 33, wherein the moldingmaterial further covers the at least one planar device, the at least oneswitching device and the at least one first capacitor.
 36. The powermodule of claim 31, wherein the molding material covers the insulatinglayer, and also covers a portion of the pins.
 37. The power module ofclaim 2, further comprising a heat sink, wherein the heat-dissipatingsubstrate is fixed on the heat sink.
 38. A power converter, comprising:a power module of claim 1; a power input terminal connected to the powermodule; and a power output terminal connected to the power module;wherein the power input terminal receives an input voltage which isconverted by the power module into an output voltage outputted throughthe power output terminal.
 39. The power converter of claim 38,comprising a heat sink which is disposed on and attached to theheat-dissipating substrate of the power module.
 40. A method ofmanufacturing a power module, the method comprising: providing a firstplanar power device, a second planar power device and a heat-dissipatingsubstrate, and disposing the first planar power device and the secondplanar power device above the heat-dissipating substrate; providing aninsulating layer, and disposing at least one planar device, at least onecapacitor and a plurality of pins on the insulting layer; covering theheat-dissipating substrate with the insulating layer, and enabling theinsulating layer to cover the first planar power device and the secondplanar power device; and connecting the first planar power device, thesecond planar power device, the at least one planar device and the atleast one capacitor to the corresponding positions.
 41. The method ofclaim 40, further comprising: covering the insulating layer with amolding material, and enabling the molding material to cover the atleast one planar device, the at least one capacitor and a portion of thepins.
 42. The method of claim 40, further comprising: disposing at leastone switching device on the insulating layer, connecting the at leastone switching device to the corresponding position; and covering theinsulating layer with a molding compound, and making the moldingcompound cover the at least one planar device, the at least onecapacitor, the at least one switching device and a portion of the pins.43. The method of claim 40, further comprising: providing a heat sink;and fixing the heat-dissipating substrate on the heat sink.
 44. Themethod of claim 40, wherein a coating or dispensing technique is used toattach solder or an adhesive to the lower surface of the first planarpower device and the lower surface of the second planar power device,and the first planar power device and the second planar power device arerespectively disposed on the heat-dissipating substrate by soldering orbonding.
 45. The method of manufacturing of claim 40, wherein theoperation of connecting the first planar power device, the second planarpower device, the planar devices and the capacitor to the correspondingpositions is performed by wire bonding or soldering.